Sundar Das disappeared for a couple of years. He told his yoga teacher, Kate Holcombe, that he was visiting his native India, and he didn’t call again until a few weeks ago. Now he’s sitting at a Middle Eastern café at the end of her block, dunking a tea bag in hot water. The two were supposed to meet at her azure home near San Francisco’s Golden Gate Park, but the steps to her front door might as well be mountains. Das is partially paralyzed on his left side.